import java.util.HashSet;

/**
 * @Author lzc
 * @Date 2023/2/23 09:18
 */
public class SetDemo {
    public static void main(String[] args) {
        /*Set<String> set = Collections.singleton("a");
        
        set.add("b");*/
    
        HashSet<String> strings = new HashSet<>();
//        strings.add("a")
    }
}
